Diagnosis of mammalian oral health often focuses on the epithelium. The epithelium is the covering of internal and external surfaces of the body, including the lining of vessels and other small cavities. It is made up of cells that are joined by small amounts of cementing substances. Epithelium is classified into different types, based on the depth of the layers and the shape of the cells residing at the surface.
The oral epithelium has a base layer of progenitor cells that are constantly replicating. As the newly replicated cells are formed at the base, they push the overlying cells toward the upper epithelial surface. As these cells approach the surface, they are flattened, eventually detached from the surface and will slough off. A healthy oral epithelium has a thickness in the range of 50–150 μm.
The first clinical symptom of an unhealthy oral epithelium is inflammation. Inflammation of the oral epithelium may result from either an increased proliferation rate of progenitor cells, a decreased detachment rate from the upper surfaces of the oral epithelium, or a combination thereof. Inflamed cell populations, including inflamed oral epithelium regions, produce cytokines that can specifically stimulate growth of evolving cancer clones. Normal epithelium populations will also respond to the chronic presence of mitogenically active cytokines by increasing their rate of cell growth. This increased cell growth is called hyperplasia. Normal epithelial cell hyperplasia can thereby be a measure of the promotional environment of a cancer clone.
The general health of the oral epithelium can sometimes be determined by visual inspection. For a more thorough diagnosis however, the thickness of the epithelium should be quantified. In order to quantify the thickness, more advanced techniques, such as endoscopy must be used.
Endoscopy is the visual inspection of a cavity of the body by use of an endoscope. An endoscope is generally a highly flexible viewing instrument that may also be capable of diagnostic and therapeutic functions. Endoscopy is widely used to diagnose, monitor and treat a number of diseases and maladies of the digestive system. Many diseases of the human digestive tract can be diagnosed by visual appearance, for example tumors possess a characteristic salmon pink color. In practice, these factors combine to allow one procedure, endoscopy, to be a relatively simple, non-surgical diagnosis and monitoring tool of many digestive tract diseases.
Use of diagnostic scopes as clinical tools was greatly advanced by the development of fiber optics in the 1950s. The use of fiber optics in diagnostic scopes allowed better images to be recorded. It also allowed more organs to be viewed because of the flexibility that fiber optics brought to the instrument. The flexibility added by fiber optics also decreased the incidence of puncturing body tissue and organs that occurred more often with rigid scopes.
Diffuse reflectance spectroscopy is a technique that was developed for use in surface analysis of powdered organic and inorganic samples. The technique is based on the diffuse reflectance of radiation that occurs when it is directed onto a surface with a matte finish or a powdered sample. The reflected radiation penetrates the sample and interacts with it before the radiation emerges from the sample as a “reflection”. While the radiation is in the sample, scattering occurs such that the diffusely reflected light emerges from the sample at all angles, as opposed to the one angle that would be observed if the scattering had not occurred.
Reflectance spectroscopy has been used previously in a clinical setting. For example, reflectance spectroscopy has been used to determine oxygen levels in the myocardium in vivo. For details of such uses see, for example, Arai, A. E., Myocardial oxygenation in vivo: optical spectroscopy of cytoplasmic myoglobin and mitochondrial cytochromes. Heart Circ. Physiol. 46: H683–H697, 1999; or Gandjbakhche, Visible-light photon migration through myocardium in vivo. Heart Circ. Physiol. 46: H698–H704, 1999.
The use of reflectance spectroscopy in the diagnosis of oral health problems would provide a noninvasive, simple and inexpensive manner of diagnosis. However, little has been done furthering the diagnosis of oral health problems using such techniques. Further, the early diagnosis of maladies, such as gum disease and oral cancer often reduces the need for painful, if not disfiguring medical intervention. Therefore, there is a need for devices and methods that utilize reflectance spectroscopy that could be used in the diagnosis of oral health problems.